[PATCH v3 1/2] USB: serial: ch314: use usb_control_msg_recv() and usb_control_msg_send()

From: Himadri Pandya
Date: Fri Oct 01 2021 - 03:00:07 EST

usb_control_msg_send/recv are new wrapper functions for usb_control_msg()
that have proper error checks for short reads. These functions can also
accept data buffer on stack. Hence use these functions to simplify error
handling for short reads. Short reads will now get reported as
-EREMOTEIO with no indication of how short the transfer was.

Signed-off-by: Himadri Pandya <himadrispandya@xxxxxxxxx>
---
Changes in v3:
- Rephrase the commit message
- Include a note on not reporting size of the short reads in the commit
- Drop unnecessary changes in ch341_control_out()
- Drop a non-relevant style change
- Remove some more "out" labels
- Remove unnecessary return statement from a void function

Changes in v2:
- Fix callers of ch341_control_out() and ch341_control_in()
- Remove label "out"
- Remove an unnecessary assignment statement
---
drivers/usb/serial/ch341.c | 90 ++++++++++----------------------------
1 file changed, 24 insertions(+), 66 deletions(-)

diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 2db917eab799..8aecc1f0dee4 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -131,23 +131,13 @@ static int ch341_control_in(struct usb_device *dev,
dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x,%u)\n", __func__,
request, value, index, bufsize);

- r = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), request,
- USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
- value, index, buf, bufsize, DEFAULT_TIMEOUT);
- if (r < (int)bufsize) {
- if (r >= 0) {
- dev_err(&dev->dev,
- "short control message received (%d < %u)\n",
- r, bufsize);
- r = -EIO;
- }
-
- dev_err(&dev->dev, "failed to receive control message: %d\n",
- r);
- return r;
- }
+ r = usb_control_msg_recv(dev, 0, request,
+ USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
+ value, index, buf, bufsize, DEFAULT_TIMEOUT, GFP_KERNEL);
+ if (r)
+ dev_err(&dev->dev, "failed to receive control message: %d\n", r);

- return 0;
+ return r;
}

#define CH341_CLKRATE 48000000
@@ -287,23 +277,18 @@ static int ch341_set_handshake(struct usb_device *dev, u8 control)
static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
{
const unsigned int size = 2;
- char *buffer;
+ u8 buffer[2];
int r;
unsigned long flags;

- buffer = kmalloc(size, GFP_KERNEL);
- if (!buffer)
- return -ENOMEM;
-
r = ch341_control_in(dev, CH341_REQ_READ_REG, 0x0706, 0, buffer, size);
- if (r < 0)
- goto out;
+ if (r)
+ return r;

spin_lock_irqsave(&priv->lock, flags);
priv->msr = (~(*buffer)) & CH341_BITS_MODEM_STAT;
spin_unlock_irqrestore(&priv->lock, flags);

-out: kfree(buffer);
return r;
}

@@ -312,30 +297,25 @@ out: kfree(buffer);
static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
{
const unsigned int size = 2;
- char *buffer;
+ u8 buffer[2];
int r;

- buffer = kmalloc(size, GFP_KERNEL);
- if (!buffer)
- return -ENOMEM;
-
/* expect two bytes 0x27 0x00 */
r = ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size);
- if (r < 0)
- goto out;
+ if (r)
+ return r;
dev_dbg(&dev->dev, "Chip version: 0x%02x\n", buffer[0]);

r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
- if (r < 0)
- goto out;
+ if (r)
+ return r;

r = ch341_set_baudrate_lcr(dev, priv, priv->baud_rate, priv->lcr);
if (r < 0)
- goto out;
+ return r;

r = ch341_set_handshake(dev, priv->mcr);

-out: kfree(buffer);
return r;
}

@@ -345,39 +325,23 @@ static int ch341_detect_quirks(struct usb_serial_port *port)
struct usb_device *udev = port->serial->dev;
const unsigned int size = 2;
unsigned long quirks = 0;
- char *buffer;
+ u8 buffer[2];
int r;

- buffer = kmalloc(size, GFP_KERNEL);
- if (!buffer)
- return -ENOMEM;
-
/*
* A subset of CH34x devices does not support all features. The
* prescaler is limited and there is no support for sending a RS232
* break condition. A read failure when trying to set up the latter is
* used to detect these devices.
*/
- r = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0), CH341_REQ_READ_REG,
- USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
- CH341_REG_BREAK, 0, buffer, size, DEFAULT_TIMEOUT);
+ r = usb_control_msg_recv(udev, 0, CH341_REQ_READ_REG,
+ USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
+ CH341_REG_BREAK, 0, &buffer, size, DEFAULT_TIMEOUT, GFP_KERNEL);
if (r == -EPIPE) {
dev_info(&port->dev, "break control not supported, using simulated break\n");
quirks = CH341_QUIRK_LIMITED_PRESCALER | CH341_QUIRK_SIMULATE_BREAK;
- r = 0;
- goto out;
- }
-
- if (r != size) {
- if (r >= 0)
- r = -EIO;
+ } else if (r)
dev_err(&port->dev, "failed to read break control: %d\n", r);
- goto out;
- }
-
- r = 0;
-out:
- kfree(buffer);

if (quirks) {
dev_dbg(&port->dev, "enabling quirk flags: 0x%02lx\n", quirks);
@@ -647,23 +611,19 @@ static void ch341_break_ctl(struct tty_struct *tty, int break_state)
struct ch341_private *priv = usb_get_serial_port_data(port);
int r;
uint16_t reg_contents;
- uint8_t *break_reg;
+ uint8_t break_reg[2];

if (priv->quirks & CH341_QUIRK_SIMULATE_BREAK) {
ch341_simulate_break(tty, break_state);
return;
}

- break_reg = kmalloc(2, GFP_KERNEL);
- if (!break_reg)
- return;
-
r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG,
ch341_break_reg, 0, break_reg, 2);
- if (r < 0) {
+ if (r) {
dev_err(&port->dev, "%s - USB control read error (%d)\n",
__func__, r);
- goto out;
+ return;
}
dev_dbg(&port->dev, "%s - initial ch341 break register contents - reg1: %x, reg2: %x\n",
__func__, break_reg[0], break_reg[1]);
@@ -681,11 +641,9 @@ static void ch341_break_ctl(struct tty_struct *tty, int break_state)
reg_contents = get_unaligned_le16(break_reg);
r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
ch341_break_reg, reg_contents);
- if (r < 0)
+ if (r)
dev_err(&port->dev, "%s - USB control write error (%d)\n",
__func__, r);
-out:
- kfree(break_reg);
}

static int ch341_tiocmset(struct tty_struct *tty,
--
2.17.1